1. Field of the Invention
The present invention relates to a terminal device and a control program thereof for three-dimensionally showing display information in a display section.
2. Description of the Related Art
Conventionally, various techniques are used to three-dimensionally (hereinafter referred to as 3D, as required) display in a flat display section display information such as images (still images and moving images), text, and menus to enable users to stereoscopically view the display information.
As a technique such as this, for example, a technique is known in which an object in two-dimensional (hereinafter referred to as 2D, as required) display information can be viewed in 3D by a visual effect that makes the object appear three-dimensional being applied to the object. A technique using a polygon is an example of this technique.
A technique is also known that uses binocular disparity between the right eye and the left eye of the user. That is, in this technique, display information for the right eye and display information for the left eye that are slightly misaligned with each other are provided, and a parallax barrier that blocks light paths is placed in an appropriate position such that, when these two display information are simultaneously shown, the display information for the right eye is visible to the right eye but not to the left eye, and the display information for the left eye is visible to the left eye but not to the right eye. As a result, the display information appears three-dimensional.
All 3D display techniques described above use a parameter referred to as 3D depth that indicates the depth of 3D or the extent of outward projection. The greater the 3D depth is the deeper or more outwardly projecting the display information appears to the user. On the other hand, the smaller the 3D depth is, the shallower or less outwardly projecting the display information appears. When the 3D depth is zero, the display information appears two-dimensional (in other words, 2D display).
When display information is shown in the display section in 3D with a predetermined 3D depth (including 2D display in which the 3D depth is zero), a method is used in which a plurality of display information having the same content but different 3D depths are provided, and from among the plurality of display information, display information having the predetermined 3D depth is selected, and the selected display information is shown in 3D. Alternatively, a method is used in which 2D display information is converted to display information having the predetermined 3D depth, and the converted display information is shown in 3D. Also, various conditions are required for 3D display to be correctly recognized by the user, and these conditions are generally stricter than the conditions for a 2D display. For example, when the display section is dark and difficult to see, 3D display is more difficult to recognize than 2D display. In addition, the distance at which 3D display is correctly recognized (the distance between the user's eyes and a screen) is limited to a shorter range than the distance at which 2D display is correctly recognized.
Conventionally, to resolve conditions such as those described above, for example, a technology is disclosed as a technology enabling 3D depth to be switched by user operation in which the depth of stereoscopic viewing is changed, and viewing is switched between stereoscopic viewing and planar viewing by user operation (refer to, for example, Japanese Patent Application Laid-Open (Kokai) Publication No. 2007-037619).
However, in the conventional technology described above, there is a problem in that the user needs to operate to switch to an appropriate 3D depth every time the situation demands it. This operation is complicated and very taxing on the user.